Jbl LX5 transform to LX7

[script56]

7897678976I have pair of JBL LX5 networks (for LE15,LE85) and want to change part s to make them LX7 specs. The LX7 is for LE14A and LE85/75. What parts would i need to replace to make it correct crossover point?e

[script56]

Above (1st) pic is LX5

[Earl K]

What you want to do is virtually impossible ( plus impractical ) for even the most accomplished ( custom coil winder ).
ie; Modifying a tapped inductor from one value to another final value all the while having different tap points ( -4db, -6db, -8db, etc ) is an almost impossible task.

You are going to need to either buy LX7 networks ( or have their special 2.57mH tapped inductors custom wound for you and then use common off-the-shelf parts for the rest of the parts seen in that LX7 schematic ).

:)

[Earl K]

Some more reading for you;

Alternatives to the Tapped Inductors in the 3110a or 3115a (http://www.audioheritage.org/vbulletin/showthread.php?33057-Alternative-to-tapped-inductor-in-3110a-or-3115a)

Autoformer Replacements (http://www.audioheritage.org/vbulletin/showthread.php?35076-DIY-Air-Core-Autofomer-Replacements-for-JBL-Crossovers&highlight=inductor)

[script56]

Does the lx7 & LX5 cross over at same point? The lx7 was to match with le14a and LX5 the le15

[Odd]

78978

[script56]

Wow. Nice chart. Since they both crossover at 500, can they be used interchangeably without damage to components?

[Earl K]

Wow. Nice chart. Since they both crossover at 500, can they be used interchangeably without damage to components?

The LF components won't be damaged ( by substituting an LX5 instead of an LX7 ).
- I can't say the same for the HF components.

FYI, both crossovers stress the compression drivers some by crossing over an octave lower than what the horns provide in terms of acoustic loading ( which is around 1000hz at cut-off ) .
- this practice is real old-school JBL stuff when amps where small tube watts and JBL could "get-away" with somewhat questionable approaches like this ( JBL eventually abandoned this type of crossover ) .

Here's a pic showing the error in response ( for an Le14H woofer ) when the LX5 is substituted for an LX7.
- ( ignore the lack of LF response below 100hz )
- ( one can see that the le14H gets robbed of some mid-band response due to the larger inductor found in the LX5 )

79005

:)

[script56]

So both LX5 & LX7 are not best option for LE85/75 based on old technology that was ok for lower watt tube amps of their day? The brochure says identical except HF attenuation is different on LX7. If the LX5 is updated with different attentuator will it make it closer to LX7 specs or must update inductors ect as Earl K describes?

[script56]

79015

[Earl K]

So both LX5 & LX7 are not best option for LE85/75 based on old technology that was ok for lower watt tube amps of their day? The brochure says identical except HF attenuation is different on LX7. If the LX5 is updated with different attentuator will it make it closer to LX7 specs or must update inductors ect as Earl K describes?

My technical pics ( plus the schematics you've previously posted ) appear to mean little to you ( hopefully others can understand their intent ).

If your crossover questions are about implementing something for your own listening pleasure ( while using a tube amp set to 1950's adult listening levels ) then consider buying a pair of used 3115a networks ( while waiting for some LX7's ) and give them a spin with your le14a/le85 components ( assuming you want to try out the low 500hz crossover point ).
- The 3115a network includes LC values ( in the low-pass section ) that are functionally pretty close to those found in the LX7.

You know, I truly doubt that the ( for instance ) Asian buyers who are after period correct JBL offerings care about what I think constitutes the design failings of JBL's older networks .
- Those Asian buyers "want what they want" and are typically willing to pay top dollar to get it ( as long as everything is correct and matches their expectations ).


:)

[script56]

No. I understand the chart. Great info. Thank you.